Trees help stabilize Buckeye Lake dam

Guest Column:

By John Sproat for Save Buckeye Lake

Trees to be removed are marked with a blue plastic dot on the lakeside of the tree. Five trees are marked to be removed between the yacht club and the regulatory spillway on North Bank. Beacon photo by Charles Prince. The Ohio Department of Natural Resources has notified Buckeye Lake embankment residents that the Division of Parks will soon be removing trees from the dam. The trees scheduled for removal have been identified by the Division of Forestry as diseased ash trees or other diseased or dangerous trees “as well as those along the dam [whose removal is] requested by adjacent homeowners.” (italics added)

While there is no objection to the removal of diseased ash and other diseased or dangerous trees, there is a serious objection to the removal of healthy, non- dangerous trees because the benefits they provide for dam stability will be lost.

In 1995, the “Save the Lake” Committee contacted Davis Sydnor PhD, Professor of Urban Forestry at OSU School of Natural Resources, to evaluate the general condition of the trees on the Buckeye Lake embankment and review the risks associated with the ODNR plan to remove all of these trees. Dr. Sydnor also conducted an inspection of each embankment tree from Lieb’s Island to the Buckeye Lake Yacht Club in 2002. No trees were found east of the yacht club.

During that later inspection Dr. Sydnor attached a numbered aluminum tag to each tree which refers to tables which identify the tree’s species, diameter at 4.5 feet in height, condition and location. Two trees (tag numbers 93 and 166) were found to present a threat to the dam. Two more trees (tag numbers 163 and 195) were considered hazardous but did not present a threat to the embankment. A summary of the conclusions and recommendations presented in both studies follows.

The Trees on the Buckeye Lake Embankment are Armoring the Dam.

Roots are well known for their ability to stabilize slopes. Woody levee cover is a critical element in increasing levee integrity. (Shields and Gray 1993) Field surveys in Missouri noted greatly increased numbers of le- vee breaks during the 1993 floods where the levees did not have woody vegetation on the levee. (Wallace et.al. 1994)

Tree Roots Grow Only 18 Inches Deep Into the Soil.

Ninety Five percent of the root system of trees is contained in the top 18 inches of soil. Roots extend 1.5 to 3 times the height of the tree from the main stem. The roots for trees that have grown successfully for decades behind the original masonry wall on the Buckeye Lake embankment grow up and down along the embankment rather than toward the new sheet pile wall and the lake. These roots help to hold the soil in place and prevent erosion.

Embankment Trees are Resistant to Windthrow.

The floodplain tree species common to Buckeye Lake are particularly well adapted to growing on the embankment. “The trees in such a site are lower growing with branches closer to the ground when compared to a forest grown tree. The root collar or trunk flair is larger, or more exaggerated, than its upland forest counterpart. This explains why I would not expect to see more windthrow of trees along the Buckeye Lake embankments .” (Sydnor 1995)

“Interestingly, removal of the lakeside trees will increase the risk of windthrow for trees behind them. These trees have developed under lower storm load conditions. I believe that this will be a significant risk to the closely spaced housing along the shore if the edge or embankment trees are removed.” (Sydnor 1995)

A Windthrown Tree is Not a Threat to the Stability of the Dam.

A windthrown tree would pull up a plug of soil and roots which would be 6-8 feet across and 12-18 inches deep. “I did not see a single instance during my site visit where the present sheet pile wall would be threatened even if a tree failed.” “Since the rootball which would be removed in a windthrow would be distant from the sheet pile wall the height of the face of the dam would remain the same. Roots lakeside of the failed tree would remain and increase the erosion resistance of the soil at the face of the embankment.” (Sydnor 1995)

Decaying Roots Lose Their Ability to Armor the Embankment

According to Dr. Sydnor, The roots of trees that have been cut down begin to decay and lose strength fairly rapidly. Therefore they lose their ability to hold the soil in place and armor the dam.

The Dodson-Lindblom Study titled “Buckeye Lake Dam Spillway Adequacy and Embankment Stability and Seepage Study”, prepared under contract with ODNR in 1987, stated, “Because of the large size of many of the trees and depth of the root systems, removal of all the trees and repair of the large holes caused by this tree removal would possibly cause more problems than if the trees were left in place.”

Summary

“Trees along the embankment are generally in good to fair condition. They are well adapted to the site and protect the trees and structures behind them. Removal would be costly, disruptive and of unproven worth. Simple adherence to good design principles will allow these trees to continue to provide shade, stabilize the soil, increase property values, armor the embankment, and modify the microclimates at minimal cost without a proven risk. (Sydnor 1995)

For these reasons embankment residents are urged to keep their healthy trees in place rather than requesting them to be cut down by ODNR, Division of Parks.